/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.bind.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Annotation for handling exceptions in specific handler classes and/or handler methods.
 *
 * <p>
 * Handler methods which are annotated with this annotation are allowed to have very
 * flexible signatures. They may have parameters of the following types, in arbitrary
 * order:
 * <ul>
 * <li>An exception argument: declared as a general Exception or as a more specific
 * exception. This also serves as a mapping hint if the annotation itself does not narrow
 * the exception types through its {@link #value()}.
 * <li>Request and/or response objects (typically from the Servlet API). You may choose
 * any specific request/response type, e.g. {@link javax.servlet.ServletRequest} /
 * {@link javax.servlet.http.HttpServletRequest}.
 * <li>Session object: typically {@link javax.servlet.http.HttpSession}. An argument of
 * this type will enforce the presence of a corresponding session. As a consequence, such
 * an argument will never be {@code null}. <i>Note that session access may not be
 * thread-safe, in particular in a Servlet environment: Consider switching the
 * {@link org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#setSynchronizeOnSession
 * "synchronizeOnSession"} flag to "true" if multiple requests are allowed to access a
 * session concurrently.</i>
 * <li>{@link org.springframework.web.context.request.WebRequest} or
 * {@link org.springframework.web.context.request.NativeWebRequest}. Allows for generic
 * request parameter access as well as request/session attribute access, without ties to
 * the native Servlet API.
 * <li>{@link java.util.Locale} for the current request locale (determined by the most
 * specific locale resolver available, i.e. the configured
 * {@link org.springframework.web.servlet.LocaleResolver} in a Servlet environment).
 * <li>{@link java.io.InputStream} / {@link java.io.Reader} for access to the request's
 * content. This will be the raw InputStream/Reader as exposed by the Servlet API.
 * <li>{@link java.io.OutputStream} / {@link java.io.Writer} for generating the response's
 * content. This will be the raw OutputStream/Writer as exposed by the Servlet API.
 * <li>{@link org.springframework.ui.Model} as an alternative to returning a model map
 * from the handler method. Note that the provided model is not pre-populated with regular
 * model attributes and therefore always empty, as a convenience for preparing the model
 * for an exception-specific view.
 * </ul>
 *
 * <p>
 * The following return types are supported for handler methods:
 * <ul>
 * <li>A {@code ModelAndView} object (from Servlet MVC).
 * <li>A {@link org.springframework.ui.Model} object, with the view name implicitly
 * determined through a
 * {@link org.springframework.web.servlet.RequestToViewNameTranslator}.
 * <li>A {@link java.util.Map} object for exposing a model, with the view name implicitly
 * determined through a
 * {@link org.springframework.web.servlet.RequestToViewNameTranslator}.
 * <li>A {@link org.springframework.web.servlet.View} object.
 * <li>A {@link String} value which is interpreted as view name.
 * <li>{@link ResponseBody @ResponseBody} annotated methods (Servlet-only) to set the
 * response content. The return value will be converted to the response stream using
 * {@linkplain org.springframework.http.converter.HttpMessageConverter message
 * converters}.
 * <li>An {@link org.springframework.http.HttpEntity HttpEntity&lt;?&gt;} or
 * {@link org.springframework.http.ResponseEntity ResponseEntity&lt;?&gt;} object
 * (Servlet-only) to set response headers and content. The ResponseEntity body will be
 * converted and written to the response stream using
 * {@linkplain org.springframework.http.converter.HttpMessageConverter message
 * converters}.
 * <li>{@code void} if the method handles the response itself (by writing the response
 * content directly, declaring an argument of type {@link javax.servlet.ServletResponse} /
 * {@link javax.servlet.http.HttpServletResponse} for that purpose) or if the view name is
 * supposed to be implicitly determined through a
 * {@link org.springframework.web.servlet.RequestToViewNameTranslator} (not declaring a
 * response argument in the handler method signature).
 * </ul>
 *
 * <p>
 * You may combine the {@code ExceptionHandler} annotation with
 * {@link ResponseStatus @ResponseStatus} for a specific HTTP error status.
 *
 * @author Arjen Poutsma
 * @author Juergen Hoeller
 * @since 3.0
 * @see org.springframework.web.context.request.WebRequest
 */
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ExceptionHandler {

	/**
	 * Exceptions handled by the annotated method. If empty, will default to any
	 * exceptions listed in the method argument list.
	 */
	Class<? extends Exception>[] value() default {};

}
